Various types of material transporting vehicles and containers use fabric to cover one or more walls. While baggage trailers and trucks are such material transporting vehicles that use fabric on one or more walls, the invention will be discussed in the environment of a cargo container, but the same concepts apply to trucks and baggage trailers.
Cargo containers have been utilized for transporting air, land and sea cargo for many years. One kind of cargo container is a box-shaped container having a plurality of closed walls and one open end or wall. The open wall forms an access opening for loading cargo into and out of the cargo container. Various types of door closures can be used across the open end for opening and closing access to the cargo container.
Both rigid door closures and flexible fabric covers have been used as door closures for cargo containers. Fabric cargo covers are generally preferred over rigid door closures because they are lighter in weight and inexpensive as compared to rigid door closures. The prior art fabric covers, for example, a standard cargo cover for an airline cargo container, are typically constructed from canvas or from vinyl coated nylon or polyester. It is not believed that such fabric was designed and engineered for use in the environment in which cargo containers are used. Disadvantages of such vinyl-coated nylon or polyester fabric cargo covers are their lack of durability to withstand the stresses and conditions to which they are subjected during use and their weight.
The "durability" of a cargo cover is determined by its tear-strength, abrasion resistance, cut-and-stab resistance and ability to withstand cold and chemical exposure. These features of cargo cover durability have not been addressed in the cargo covers of the prior art made from vinyl-coated nylon or polyester. For example, standard airline cargo covers made from a vinyl-coated nylon having a weight of 18 oz. per square yard; a tear-strength of only approximately 250 lbs.; a dead tear-strength of as little as 50 lbs.; limited abrasion and abrasion resistance; and practically no cut-and-stab resistances. Because of the cover's lack of durability the fabric covers quickly become torn during use, resulting in the covers having a limited product life. The product life, for instance, of typical airline cargo cover is less than one year. When used in seagoing containers, because of the saltwater and atmosphere, this product life may be less.
The limited product life of a prior art fabric cargo cover is often the result of inadvertent or intentional ripping or tearing. For example, forklifts are often used to load and unload cargo containers onto rail cars, trucks and boats. The tines of the forklift often tear the fabric cargo covers when they are inadvertently maneuvered against the fabric cover during the loading process. The fabric cargo cover's lack of tear strength and cut resistance also makes the contents of the cargo container susceptible to theft. For instance, an employee or other individual can easily use a pocketknife to cut open presently available fabric covers to remove the cargo.
The problem of the lack of strength and cut resistance of prior art fabric cargo covers has been noted in one instance in the prior art. U.S. Pat. No. 4,538,663 to Looker discloses a new design for a cargo cover intended to address the lack of tear-strength of conventional fabric cargo covers. However, no change to the fabric material itself are disclosed. The Looker cargo cover includes a protective cable system extending across a conventional fabric. Adding cables to protect a fabric cargo even further increases the weight and expense.
In addition to durability and strength characteristics, the weight of a fabric cargo cover should be minimized to help limit the gross weight that is being transported. The vinyl-coated nylon or polyester, however, is a relatively heavy material. Any additional weight added to the gross cargo weight results in increased fuel consumption and costs to transport the cargo.